Your car's battery light is an indicator of when your car's charging system is malfunctioning. This can be a result of a malfunctioning alternator, a battery going bad, or a number of other things. It's important to know how to respond when your car's battery light goes on: stay calm, check your vehicle gauges, and reduce power until you're able to have an auto mechanic check for possible problems. It may be a serious situation or a simple one, but it's a situation requiring action just the same.

Steps

1

Resist the urge to panic. When your battery light comes on, it sometimes results in a very simple solution.

2

Look at your gauges. Check the gauge that indicates the vehicle's state of charge, called the voltmeter (be aware that not all cars have this gauge). Often, this gauge has a picture of a battery on it. If it is extremely high or low, it's something to worry about. Normal operating range is 12 to 14 volts. If it is measuring about the same as it always does, you probably don't have a major problem.

3

Reduce the power you are using by shutting off consumers that are not needed. Examples are the radio, fan blower, defroster, dome light. Refrain from using power windows, if possible.

4

Keep your engine running. You may not be able to restart the motor if you turn the car off. If there is an alternator failure you will be running on the car's battery which may last about a half hour. As your car's engine runs, the battery may continue to charge, depending on the failure. Additionally, one of the biggest battery drains is starting your car. By not having to start the engine after shutting it off, you're not using any additional power that might be running low.

5

Drive to an auto mechanic shop or local parts store. Ask someone to help you test your alternator. If your alternator is fine, ask them to check your battery. The light could be an indicator of a battery going bad or a faulty sensor.

6

Check the battery cables. If they appear corroded or loose, that might be your problem. Clean the cables and the battery terminal with a wire brush. Tighten the cables on your battery terminals.

7

Examine your alternator belt. If it is loose, tighten it or buy a new one. If it is cracked, buy one immediately. If your alternator belt breaks, your car will not charge.

8

Restart your car after at least five minutes. On newer cars, this will help your car reset its computer system. After it has reset, the battery light may go off. It may have just been a temporary trigger or sensor. If it returns you, will need to have it looked at by a mechanic.

9

Check with an auto mechanic if all of these steps fail to reveal the true problem. Your car's computer system has many sensors and warning indicators. It is likely a computer system issue.

My battery light came on while driving and there is a whining noise. Is it the alternator?

wikiHow Contributor

The alternator can sometimes make a whining sound a few times before it goes--that is when your car battery light comes on as a sign that it is now completely faulty and needs replacing. It is usually the accessory or serpentine belt that is built inside the alternator that makes that type of noise. You need to get your car evaluated by a qualified mechanic and get him to look at your alternator.

My car battery indicator is red when I insert the key, but it turns off after I start the engine. I replaced the battery just a day ago. What could be wrong?

Logic Johnson Lafontaine

There is nothing wrong. The red battery indicator is just your car telling you it's running on battery power, which is completely normal if the engine isn't on. When you start the engine, your power comes from the alternator, so the battery light is supposed to turn off. If the battery light stayed on after you started the engine, that would be bad. It would mean you have an alternator problem.